Abstract

Local flow patterns determine the uneven distribution of atherosclerotic lesions. This research aims to elucidate the mechanism of regulation of nuclear translocation of Yes-associated protein (YAP) under oscillatory shear stress (OSS) in the atheroprone phenotype of endothelial cells (ECs). We report here that OSS led to tyrosine phosphorylation and strong, continuous nuclear translocation of YAP in ECs that is dependent on integrin α5β1 activation. YAP overexpression in ECs blunted the anti-atheroprone effect of an integrin-α5β1 blocking peptide (ATN161) in Apoe-/- mice. Activation of integrin α5β1 induced tyrosine, but not serine, phosphorylation of YAP in ECs. Blockage of integrin α5β1 with ATN161 abolished the phosphorylation of YAP at Y357 induced by OSS. Mechanistic studies showed that c-Abl inhibitor attenuated the integrin α5β1-induced YAP tyrosine phosphorylation. Furthermore, the phosphorylation of c-Abl and YAPY357 was significantly increased in ECs in atherosclerotic vessels of mice and in human plaques vs. normal vessels. Finally, bosutinib, a tyrosine kinase inhibitor, markedly reduced the level of YAPY357 and the development of atherosclerosis in Apoe-/- mice. The c-Abl/YAPY357 pathway serves as a mechanism for the activation of integrin α5β1 and the atherogenic phenotype of ECs in response to OSS, and provides a potential therapeutic strategy for atherogenesis.

Abstract

The aortic root is the predominant site for development of aneurysm caused by heterozygous loss-of-function mutations in positive effectors of the transforming growth factor-β (TGF-β) pathway. Using a mouse model of Loeys-Dietz syndrome (LDS) that carries a heterozygous kinase-inactivating mutation in TGF-β receptor I, we found that the effects of this mutation depend on the lineage of origin of vascular smooth muscle cells (VSMCs). Secondary heart field–derived (SHF-derived), but not neighboring cardiac neural crest–derived (CNC-derived), VSMCs showed impaired Smad2/3 activation in response to TGF-β, increased expression of angiotensin II (AngII) type 1 receptor (Agtr1a), enhanced responsiveness to AngII, and higher expression of TGF-β ligands. The preserved TGF-β signaling potential in CNC-derived VSMCs associated, in vivo, with increased Smad2/3 phosphorylation. CNC-, but not SHF-specific, deletion of Smad2 preserved aortic wall architecture and reduced aortic dilation in this mouse model of LDS. Taken together, these data suggest that aortic root aneurysm predisposition in this LDS mouse model depends both on defective Smad signaling in SHF-derived VSMCs and excessive Smad signaling in CNC-derived VSMCs. This work highlights the importance of considering the regional microenvironment and specifically lineage-dependent variation in the vulnerability to mutations in the development and testing of pathogenic models for aortic aneurysm.

Abstract

Non-coding RNAs are emerging as important players in gene regulation and disease pathogeneses. Here, we show that a previously uncharacterized long non-coding RNA, NEXN-AS1, modulates the expression of the actin-binding protein NEXN and that NEXN exerts a protective role against atherosclerosis. An expression microarray analysis showed that the expression of both NEXN-AS1 and NEXN were reduced in human atherosclerotic plaques. In vitro experiments revealed that NEXN-AS1 interacted with the chromatin remodeler BAZ1A and the 5′-flanking region of the NEXN gene, and upregulated NEXN expression. Augmentation of NEXN-AS1 expression inhibited toll-like receptor-4 oligomerization and NFκB activity, downregulated the expression of adhesion molecules and inflammatory cytokines by endothelial cells, and suppressed monocyte adhesion to endothelial cells. These inhibitory effects of NEXN-AS1 were abolished by knockdown of NEXN. In vivo experiments of ApoE knockout mice fed a Western high-fat diet demonstrated that NEXN deficiency promoted atherosclerosis and increased macrophage abundance in atherosclerotic lesions, with heightened expression of adhesion molecules and inflammatory cytokines, whereas augmented NEXN expression deterred atherosclerosis. A group of patients with coronary artery disease were found to have lower blood NEXN levels than healthy individuals. These results indicate that NEXN-AS1 and NEXN represent potential therapeutic targets in atherosclerosis related diseases.

Abstract

Activation of the type 1 angiotensin II receptor (AT1) triggers proinflammatory signaling through pathways independent of classical Gq signaling that regulate vascular homeostasis. Here, we report that the AT1 receptor preformed a heteromeric complex with the receptor for advanced glycation endproducts (RAGE). Activation of the AT1 receptor by angiotensin II (Ang II) triggered transactivation of the cytosolic tail of RAGE and NF-κB–driven proinflammatory gene expression independently of the liberation of RAGE ligands or the ligand-binding ectodomain of RAGE. The importance of this transactivation pathway was demonstrated by our finding that adverse proinflammatory signaling events induced by AT1 receptor activation were attenuated when RAGE was deleted or transactivation of its cytosolic tail was inhibited. At the same time, classical homeostatic Gq signaling pathways were unaffected by RAGE deletion or inhibition. These data position RAGE transactivation by the AT1 receptor as a target for vasculoprotective interventions. As proof of concept, we showed that treatment with the mutant RAGE peptide S391A-RAGE362–404 was able to inhibit transactivation of RAGE and attenuate Ang II–dependent inflammation and atherogenesis. Furthermore, treatment with WT RAGE362–404 restored Ang II–dependent atherogenesis in Ager/Apoe-KO mice, without restoring ligand-mediated signaling via RAGE, suggesting that the major effector of RAGE activation was its transactivation.

Abstract

Emerging evidence indicates that angiopoietin-2 (Angpt2), a well-recognized vascular destabilizing factor, is a biomarker of poor outcome in ischemic heart disease. However, its precise role in postischemic cardiovascular remodeling is poorly understood. Here, we show that Angpt2 plays multifaceted roles in the exacerbation of cardiac hypoxia and inflammation after myocardial ischemia. Angpt2 was highly expressed in endothelial cells at the infarct border zone after myocardial infarction (MI) or ischemia/reperfusion injury in mice. In the acute phase of MI, endothelial-derived Angpt2 antagonized Angpt1/Tie2 signaling, which was greatly involved in pericyte detachment, vascular leakage, increased adhesion molecular expression, degradation of the glycocalyx and extracellular matrix, and enhanced neutrophil infiltration and hypoxia in the infarct border area. In the chronic remodeling phase after MI, endothelial- and macrophage-derived Angpt2 continuously promoted abnormal vascular remodeling and proinflammatory macrophage polarization through integrin α5β1 signaling, worsening cardiac hypoxia and inflammation. Accordingly, inhibition of Angpt2 either by gene deletion or using an anti-Angpt2 blocking antibody substantially alleviated these pathological findings and ameliorated postischemic cardiovascular remodeling. Blockade of Angpt2 thus has potential as a therapeutic option for ischemic heart failure.

Abstract

The M2 isoform of pyruvate kinase (PKM2) is highly expressed in most cancer cells, and has been studied extensively as a driver of oncogenic metabolism. In contrast, the role of PKM2 in nontransformed cells is little studied, and nearly nothing is known of its role, if any, in quiescent cells. We show here that endothelial cells express PKM2 almost exclusively over PKM1. In proliferating endothelial cells, PKM2 is required to suppress p53 and maintain cell cycle progression. In sharp contrast, PKM2 has a strikingly different role in quiescent endothelial cells, where inhibition of PKM2 leads to degeneration of tight junctions and barrier function. Mechanistically, PKM2 regulates barrier function independently of its canonical activity as a pyruvate kinase. Instead, PKM2 suppresses NF-kB and its downstream target, the vascular permeability factor angiopoietin 2. As a consequence, loss of endothelial cell PKM2 in vivo predisposes mice to VEGF-induced vascular leak, and to severe bacteremia and death in response to sepsis. Together, these data demonstrate new roles of PKM2 in quiescent cells, and highlight the need for caution in developing cancer therapies that target PKM2.